| Acetic acid | A bacterial byproduct, sour-tasting acetic acid is common in sour beer styles such as Flanders red ales, which are open-fermented to welcome such funk-inducing compounds. In most styles, though, acetic acid is an off flavor; it’s detectable by a green apple, vinegar or paint aroma and/or flavor. Its most common cause is a contamination in the brewing process or your pub’s tap system. |
